I studied ancient Egypt, and pre-Islamic religion has always interested me as a possible source of comparison, however I'm not an expert on it. Someone else can add/correct/subtract to this.

Obviously Islam covers many countries in the Mediterranean. As you say, the average person knows quite a bit about Egyptian religion, but not so much elsewhere in what is now the Muslim world. Someone posted about Zoroastrianism, which was a prominent pre-Islamic religion in what is now mostly Iran.

Probably the most interesting group is what existed in the Arabian Peninsula. This is generally called 'Arabian religion' or 'pre-Islamic Arabian'. Much of this religion is similar to other religions of the time - it has a number of deities, associated myths, as well as spirits that are seen as evil or good or bivalent. One of these deities was Allah, who was always a creator god and main figure in the pantheon. 'Allah' literally means 'the god'. See here

As for why the average person (even the average historian) doesn't know about this is because of the nature of the religion, the way it was replaced, and the way it is recorded.

The most interesting thing (at least for me) is how pre-Islamic Arabian religion wasn't really 'wiped out' by Islam so much as it was 'sucked into' it. For example, we know that spirits (jinn) were a large part of the religion, and these are still believed today as a sort of parallel belief system to Islam.

You see this in other countries, e.g., parts of eastern Europe still have folk religions that sort of slot into quite Christian world views. As another example, we think that the Kaaba - the centre of Mecca - was actually a pre-Islamic cult location. This sort of appropriation is of course common across all religions, and is important to remember as context.

So I guess what I'm saying is that there was no clash of civilisations that made pre-Islam famous in the same way that, for example, the spread of Islam (or Christianity) into other places saw.

A second part is that - as far as we know - pre-Islamic religion wasn't as formalised, institutionalised, or centralised the same way that modern religions are. Because of this, there appears to be large variations of the religion over time and place. Obviously, most pre-modern religions were actually like this, however the diversity that you find in pre-Islamic Arabia is pretty startling.

The last piece of this puzzle is the remains of the religion. As I said before, a lot of pre-Islamic Arabian religion still exists as a sort of localised folklore. Belief and narratives of jinn are a good example of this. We do have some archaeology, art, and language from the time, which you can get an intro into here, that give insight into the religion.

Large collections of records of the religion, though, can actually be found in Yemen. As you can imagine, Yemen hasn't been a popular destination for archaeologists, which is a shame, as it was a centre of the Sabaeans - a group of people who who had extensive contact in the Horn of Africa (another place that needs further work).

I've never found one book on this topic that is very accessible, to be honest. The Camel and the Wheel is engaging, but a bit out-dated and can be parochial. I tried reading Arabia and the Arabs: From the Bronze Age to the Coming of Islam, and it seemed very well-referenced, but not something the ordinary person would read cover-to-cover. There is good, recent, scholarship about ancient Yemen (a topic I highly recommend), as historians seem to have re-discovered it alongside its importance as a regional player with the Horn of Africa.

Hope some of that helps!

There's an FAQ about religion in the Arab world before Islam that might be interesting to you.

This honestly depends on the time period but if your on about religion just before, then a fair bit is known.

A book called Kitab al-ansam or the book of idols describes a statue of a God with a golden hand near the Kaaba which was called Hubal.

He was the chief God of an entire pantheon the book which goes on to describe his daughters the pantheon foes and spirits which include Jinn which can be good or evil.

It is also worth noting that some tribes practiced a form of Gnosticism or Judaism before conversion to Islam. And some people still practice a form of the original religion, not many as the pressure to convert is a strong one.

Another book is by Gaston Maspero Called the dawn of civilization this backs up the book of idols but it's more broad as it covers lots of areas.

The Quran 7:11-12 also mentions the previous people.

Semi-related, but anyone interested in pre-Islam Arabia might want to check out the Roads of Arabia exhibition. That's the link to the DC exhibit (which closed about a year ago) but it has some interesting background and some exhibit highlights. I wasn't able to find more on it-I'm on my phone-but what little is available is really, really interesting (the exhibit itself was fascinating, if it's near anyone right now!)